Pile-to-jacket connector



ay 19, 1970 J. BARDGETTE ,5 1

PILE-TO-JACKET CONNECTOR Filed Jan. 22, 1968 FiG.6.

INVENTDRS F JOHN J. BARDGETTE, WILLIAM J. RUEZ,I[L,

ATTORNEY.

United States Patent 3,512,811 PILE-TO-JACKET CONNECTOR John J. Bardgette, New Orleans, and William J. Ruez III and Luther S. Moody, Metairie, La., assignors to Esso Production Research Company Filed Jan. 22, 1968, Ser. No. 699,461 Int. Cl. F161 13/02 US. Cl. 285--286 4 Claims ABSTRACT OF THE DISCLOSURE A single ring connector of variable wall thickness for joining an outer pipe (e.g., platform jacket leg) to an inner pipe (e.g., platform pile) for load transfer purposes. In the erection of an offshore structure, a pile member is inserted through each jacket leg of the substructure; and after the substructure is positioned on the sea floor each pile member is driven into the sea floor; and then a pile-tojacket connector is lowered over the top of each pile member and welded to the jacket leg and to the pile member.

BACKGROUND OF THE INVENTION The present invention generally concerns the design and construction of offshore platforms which use jackettype substructures common to the oil industry. More particularly, the invention concerns a special piling-to-jacket connector and method of installation thereof.

Tubular steel piles are normally driven through steel jacket legs which comprise the substructure for offshore platforms. After the piles are driven to refusal they are connected at the tops of the jacket legs only. Such a connection between each jacket leg and the pile associated therewith has commonly been made by inserting one or more layers of plate section into the annular space between the outer surface of the pile and the inner surface of the jacket leg and then welding these components together with fillet welds. The load is transferred from the jacket leg through the fillet welds into a series or family of plates and from these plates into the piles through more fillet welds. In general, the load transfer produces shear forces in the fillet welds and tensile forces in the plates.

To minimize the need for close dimensional control during fabrication of piling and jacket legs and to facilitate pile driving operations during erection of offshore platforms, ample clearance is provided between the outer surface of a pile and the inner surface of a jacket leg. It has been necessary to have available at the erection site several thicknesses of plate so that field erection crews could select plates to fill the annulus and provide correct fits for welding because of the normally accepted dimensional tolerances for rolling or fabricating steel pipe and because of the need for proper spacing between pieces of steel to obtain effective welds. The effective strength of this type connection is limited to the strength that can be developed by the thinnest plate and thus becomes a determining .factor in selecting the size of the annular space. This in turn determines the internal diameter of the jacket leg at this connection. Since the load transferred by this connection is not known at the start of design, such dimesions must be assumed and then later corrected if found inadequate.

The present invention provides for transfer of load from the jacket leg through a full strength butt weld into a special pileto-jacket connector and from such special connector to the pile through a continuous fillet weld. No initial dimension assumption concerning the pile-to-jacket connection is required. After the load to be transferred from the jacket to the pile is determined, the special connector can be properly sized for that particular load. Since "ice no field erection choice is required, the possibility of field misinterpretation of designer intent is eliminated. In addition, the family of plates is also eliminated.

SUMMARY OF THE INVENTION Briefly, the invention comprises a connector for use in connecting an outer pipe to an inner pipe comprising a ring member having a variable wall thickness and a uniform outside diameter adapted to bridge the annular space between the inner and outer pipes and to be connected at one end to the inner pipe and at the other end to the outer pipe, the inner diameter of said one end of said connector being slightly greater than the outer diameter of said inner pipe and the inner diameter of the other end being substantially the same as the inner diameter of the outer pipe.

The invention also includes a method for use in erecting a structure which comprises the steps of positioning an outer pipe which comprises a part of the substructure of an offshore platform on the ocean floor; sliding an inner pipe within the outer pipe; sliding a ring member having a variable inside diameter over said inner pipe until said ring member is adjacent one end of said outer pipe, one end of said ring member having a diameter slightly larger than the outer diameter of said inner pipe and said other end of said ring member having an inner diameter substatially the same as the inner diameter of said outer pipe; and then welding said one end of said ring member to said inner pipe and said other end of said ring member to said outer pipe.

Thus, a primary object of the invention is to provide an improved connector for transfer of loads in offshore structures and the method of installation thereof.

BRIEF DESCRIPTION OF THE DRAWING The above object and other objects and advantages of the invention will be apparentfrom a more detailed description of the invention when taken with the drawings wherein:

FIG. 1 is a schematic elevation of an offshore platform erected in accordance with the present invention;

FIG. 2 is an enlarged, more detailed view of the jacket-to-pile connection shown in FIG. 1;

FIG. 3 is a view of a modified jacket-to-pile connector;

FIG. 3A illustrates various shaped plug welds usable in the type packet-to-pile connector illustrated in FIG. 3;

FIG. 4 is a view of another modification of the jacketto-pile connection;

FIG. 5 is a fragmentary view of a different configuration for the jacket-to-pile connection of FIG. 4; and

FIG. 6 is a fragmentary view of still another configuration for the jacket-to-pile connection of FIG. 4.

Referring to FIG. 1 of the drawing, there is illustrated an offshore platform 10 supported by a superstructure including deck or platform supporting legs 11 and structural bracing 12 and a substructure 13 including jacket legs 14 through which piles 15 extend. Structural bracing 16 is also provided. The lower end of each pile 15 ex tends through each jacket leg 14 into the ocean floor 21. The upper end of each pile 15 connects to the lower end of leg 11 of the superstructure. A jacket-to-pile connector connects each jacket leg 14 to the pile 15 extending through it. A minimum of three jacket legs 14 and piles 15 may be used but preferably four each of such structural elements are used.

The jacket-to-pile connector 25 is seen in greater detail in FIG. 2. As shown in that figure, connector 25 comprises a ring member having a substantially uniform outside diameter and a variable Wall thickness. The upper inner diameter indicated at 26 is slightly larger than the outside diameter of pile 15. The lower inside diameter indicated at 27 tapers outwardly until the diameter of the ring member at the lower end thereof is substantially the same as the inside diameter of jacket leg 14 as indicated at 28.

In erecting the offshore structure, the substructure 13 including the jacket legs 14 and bracing 16 are set on the ocean floor 21. A pile 15 is then driven through each jacket leg into the ocean floor with the upper end thereof extending above the upper end of jacket leg 14. Sufficient annular space is provided between pile 15 and the inner diameter of jacket leg 14 to permit driving the pile therethrough in this manner within normal construction tolerances. A connector 25 is then slipped over each of the piles 15 and lowered until the lower end thereof contacts the top of the jacket leg. The lower periphery of ring member 25 is welded to the upper end of jacket leg 14 with butt welds as indicated at 29 and the upper end of ring member 25 is welded to pile 15 with a fillet weld as indicated at 30. Deck support legs 11 which are the same size as piles 15 are set on top of the driven piles 15 and welded to them with butt welds as indicated at 31. Horizontal loads received by the platform from waves, wind or marine vessels docking against the platform are transmitted to piles through the ring connectors 25.

Connector is attached to the jacket leg 14 by a butt weld equivalent in strength to the jacket leg and is attached to the pile 15 by a fillet weld of sufiicient size and length to develop the strength required for load transfer. There are many alternative weld configurations that can be used. The configuration illustrated in FIGS. 1 and 2 is the most economical weld provided the load to be transferred from the jacket leg to the pile is small. If the quantity of weld provided by such an arrangement is not adequate,

then additional capacity can be gained by adding plug welds (a type of fillet weld) of a desired shape such as those illustrated in FIGS. 3 and 3A. As shown in those figures, ring connector 25A is provided with a plurality of spaced apart slots. The side surfaces of these slots are attached to pile 15 by additional fillet welds (e.g. plug welds). As shown in FIG. 3, slot is elliptically shaped. In FIG. 3A, other slot and plug weld configurations are illustrated. A circular configuration is illustrated at 38, a (rectangular) square, or diamond configuration is illustrated at 39 and a triangular configuration is illustrated at 40.

If the load is such that the addition of plug Welds is not adequate, the scalloped shapes such as those illustrated in FIGS. 4, 5 and 6 for the connection between connector 25 and pile 15 may be used. In FIG. 4, the upper end of connector 25B is provided with a series of spaced apart rectangularly configured indentations which are suitably welded to pile 15 as at 46. In FIG. 5, a sawtooth configuration 47 is illustrated for the connector 25C. In FIG. 6, a rounded sawtooth configuration 48 is illustrated for a connector 25D. The rounded intersection sawtooth 48 is preferred because the sawtooth shape provides a superior load transfer efficiency and stress concentration is mitigated. The pointed intersections for the rectangular shape and sawtooth shape create undesirable stress concentrations. Consequently, rounded intersections are preferred in practice. The sawtooth shape has greater load transfer efiiciency than rectangular shape because maximum available cross-section of plate is utilized.

Having fully set forth the apparatus, method, objects and advantages of our invention, we claim:

1. A coupling connecting a larger diameter jacket leg, the lower end of which is adapted to be located on the sea floor and the upper end of which is adapted to be located above the surface of the water, to a smaller diameter driven pile extending through said jacket leg comprising:

a ring member having a variable wall thickness bridging the annular space between said jacket leg and said pile, the upper end of said ring member being scalloped and welded to said pile and the lower end of said ring member being welded to the upper end of said jacket leg, the outer diameter of said ring member being uniform and the inner diameter of the upper end of said ring member being slightly larger than the diameter of said pile and the inner diameter of the lower end of said ring member being substantially the same diameter as the inner diameter of said jacket leg;

said ring member also having at least one slot, the side surfaces of which are attached to said pile by welds.

2. A coupling connecting a larger diameter offshore platform jacket leg, the lower end of which is adapted to be located on the sea floor and the upper end of which is adapted to be located above the surface of the water, to a smaller diameter driven pile extending through said jacket leg comprising a ring member having a variable wall thickness bridging the annular space between said jacket leg and said pile, the upper end of said ring member being welded to said pile and the lower end of said ring member being welded to the upper end of said jacket leg, the outer diameter of said ring member being uniform and said inner diameter of said upper end of said ring member being slightly larger than the diameter of said pile, and the inner diameter of the lower end of said ring member being substantially the same as the inner diameter of said jacket leg.

3. A coupling as recited in claim 2 in which said upper end of said ring member is scalloped.

4. A coupling as recited in claim 2 in which said upper end of said ring member is scalloped in a rounded sawtooth configuration.

References Cited UNITED STATES PATENTS 1,700,319 1/1929 Kjekstad 285-286 1,853,549 4/1932 Clark 285-286 X 2,154,407 4/1939 Miller 285286 X 2,562,294 7/1951 Cohenzli 285177 3,068,026 12/1962 McKamey 285l77 X 3,163,449 12/1964 Westfall 285-286 X 2,429,952 10/1947 Willey 61-46 FOREIGN PATENTS 1,260,714 4/ 1961 France. 1,415,620 9/1965 France.

DAVE W. AROLA, Primary Examiner US. Cl. X.R. 6146, 53 

